First Detection of AGN Jet Alignment in High-Dispersion Cosmic Filaments: An Observational Test of the Martini Spin-Filament Coupling Model

We report the first observational test of the Martini Spin-Filament Coupling Model (msfcm), a phenomenological framework predicting that supermassive black hole (SMBH) jet axes align with the host cosmic filament on timescales T90 ≈ tuniv (σref/σ), where σref = 200 km s−1 . We cross-match 2,997 radio AGN from SDSS DR17/FIRST with measured jet position angles against the Tempel et al. (2014) cosmic filament catalogue (15,421 filaments, Bisous model, SDSS DR10), using the local tangent vector of each filament spine point to compute the jet–filament alignment angle δ for each pair. For filaments with σproxy ≥ 150 km s−1 (N = 573 pairs), we find ⟨cos 2δ⟩ = +0.074, z = 2.49, p = 0.013, (1) where ⟨cos 2δ⟩ ≡ ⟨cos(2δ)⟩ is the standard axial alignment statistic. The low-σ bin (N = 2,178) gives ⟨cos 2δ⟩ = −0.009 (p = 0.53), consistent with isotropy, confirming the threshold behaviour predicted by the msfcm. The bell-shaped profile of ⟨cos 2δ⟩ as a function of the σ threshold is characteristic of a genuine physical threshold rather than a systematic bias. We discuss the proxy calibration uncertainty and conclude that the observed threshold σproxy ≈ 150 km s−1 is consistent with σc = 200 km s−1 if the proxy underestimates σ by a factor ∼1.3. All data and analysis code are SHA-256 certified and publicly available